A very wide range of metal alloys are used for different applications, each alloy offering a particular combination of properties, including strength, ductility, creep resistance, corrosion resistance, fatigue resistance and castability. Alloys are commercially available in a number of physical forms and purities, depending upon the requirements of the end-application. Most large end-use metals and alloys are deliverable in sheet, rod and bar form, with an increasing number becoming available in the form of high quality powders for application within powder metallurgical processes. These processes allow manufacture, for example, of parts with complex geometries and avoid excessive machining and hence waste of expensive bulk alloy. It also allows manufacture of parts in a more diverse range of alloys than is commonly used within the larger industrial businesses.
Using the titanium industry as an example, the global production of titanium is relatively small and the majority of titanium currently produced finds use within the aerospace industries, predominantly as a very limited selection from the commonly accepted ASTM “grades” of titanium and titanium alloys. Other industries, however, have encountered difficulties in sourcing the titanium alloy they require and many suppliers and manufacturers find it undesirable to maintain a large stock of a range of different titanium alloys as a result of the high price of titanium. The shortage of supply of titanium and the dominance of Ti-6Al-4V as the standard “workhorse” alloy means that commercialization of alternative alloy formulations, and even the use of the standard accepted alloy grades, can be stifled.
For example, although pure titanium is highly resistant to corrosion, its corrosion resistance can be improved by forming an alloy with precious metals such as palladium and/or ruthenium. Likewise, the corrosion resistance of Ti-6Al-4V may be similarly improved by the addition of palladium or ruthenium. These precious metal-modified alloys are listed, along with many others, within the commonly accepted ASTM grades of titanium alloys. These alloy grades find only limited application, due in part to both their poor availability and also to the additional expense of the precious metal. Machining of standard alloy forms to complex geometries, and the resulting wasted material, further increases the expense. Improvements in powder metallurgical processing, and especially a flexible method to incorporate the precious metal, would lead to the ability to manufacture parts and exploit the beneficial alloy properties whilst minimizing expense.
Cermets have been designed so that they display characteristics of both the ceramic and metallic components. In this regard, the ceramic component may contribute a high temperature resistance and hardness, while the metal component can contribute plastic deformation. Cermets have found use in the electronic industry (in the manufacture of resistors and capacitors), ceramic-to-metal joints and seals, as well as in medical applications, such as dentistry.